CHINO HILLS - The cost to install underground transmission lines through the city would far exceed that to build a line above ground, according to a Southern California Edison preliminary report.

The estimated costs for five proposed underground transmission configurations for the Chino Hills segment of the Tehachapi Renewable Transmission Project range from about $486 million to $807 million, according to Edison. The costs are preliminary and subject to change, company spokesman Paul Klein said.

Constructing an above- ground transmission line through Chino Hills would cost $172 million, according to the Edison report.

The California Public Utility Commission asked Edison to investigate alternatives to the line in 2011 after Chino Hills filed a petition protesting the above-ground portion of the project in the city.

City officials have spent more than $2million trying to stop the installation of the 200-foot-high, 500-kilovolt towers through Chino Hills. The power lines are part of Edison's 173-mile Tehachapi Renewable Transmission Project.

"We've been planning to complete the project in 2015 for quite some time, and several of the generators that are planning to connect the project are relying on areas to be completed to deliver energy to the load," said Charles Adamson, the principal manager of construction projects for Edison.

"So if the TRTP is not completed on or about the end of 2015, it starts to have impacts to those generators."

Edison's testimony was submitted this week to the Public Utility Commission as part of requested testimony. The commission will make the final decision on whether to put the lines underground.

The five underground lines are estimated to cost $807 million, $620 million, $566 million, $540 million and $486 million.

Building them underground would also mean abandoning $16 million spent on construction costs and an additional

$2 million to remove towers built in the past year, Edison officials said.

Nearly a dozen towers would have to be dismantled and removed if the commission decides to place the line underground, Adamson said.

The power company would not be able to use any of the dismantled towers anywhere else, he said.

Chino Hills officials and some residents have called for an alternate route around the city, or underground along the easement, citing concerns over aesthetic degradation, decreased home values and safety.

Bob Goodwin, who helps coordinate the Hope for the Hills resident opposition group based in Chino Hills, said undergrounding is a viable option.

"Edison is making it out to be much worse and more costly than it is because, plain and simple, they simply don't want to do it," Goodwin said.

Opponents to the project will get a chance to present their own testimony on Edison's report in 2013.

The commission is expected to make a decision in July on whether to build the lines underground.

If the commission approves an underground option, Edison officials said they hope to have work completed by late 2015 in order to meet contract requirements related to the generators, Adamson said.

If approved, the underground power lines through Chino Hills would be an engineering first for North America, Edison said.

"These estimates do not account for the substantial risk of unexpected delays during construction of an underground configuration, should the commission adopt an underground design," according to Edison's report.

"There is no experience with 500kV underground cable installation and operation in North America, and therefore no realistic predictors of the time it will take to successfully design, procure, manufacture, delivery, install and test the 500kV infrastructure."

Klein said it would be premature to comment on whether moving the lines underground would mean higher energy rates.